A crane normally has not only a drive for at least one hoisting unit for hoisting a load, but also one or more drives for carrying out crane movements. Examples of such crane movements are adjustment of the inclination of the boom of the crane and especially swiveling movements of the boom about a vertical axis of rotation. The given drives are actuated via manual input devices, which are usually designed in the form of control levers. The speed of the given drive linked with the control level can be adjusted as desired to variably large values by variable displacement of the control lever.
Modern cranes are normally provided with an electronic control system, which receive their control commands via the aforementioned manual input devices and convert them to corresponding signals for controlling the drives. In order to guarantee uniform factory-set system performance, it is customary to compensate tolerances of mechanical and electronic components, which would lead to different system performance in the individual cranes, by suitable adjustment of their action, so that practically the same performance can be guaranteed in each device of a crane type. This means that, as a result of the adjustment, when a manual input device is operated in a certain way, the given drive always responds in the same way, independently of which device of the given type is presently being used. This eliminates the need for the crane operator to go through a learning phase to adjust to the performance of a crane that is new to him when he changes between individual cranes.
The requirements on the operability of a crane can sometimes vary greatly, depending on the specific application. In the case of the lifting of relatively small loads at construction sites, one is often primarily interested in high operating speeds and less on carrying out exact positioning maneuvers. Just the opposite is true in the case of assembly work, which depends on exact positioning of the suspended load, which is often very heavy, and less on especially fast execution of the work. With previously known crane control systems, it has not been possible to take into account the varying skill levels of crane operators with respect to operating the manual input devices for controlling the crane drives for different applications with the most effective sensitivity.